The present invention relates to a movable chair suitably used by a person physically handicapped by his/her legs, loins, or the like and, more particularly, to an improvement in a folding mechanism allowing a physically handicapped person to mount/dismount on/from the movable chair by his/her own strength, traveling devices for the movable chair, a direction change device for the movable chair, and the like.
For a person who is physically handicapped by his/her legs or loins and cannot stand or walk by his/her own strength, a movable chair such as a wheelchair is indispensable to indoor and outdoor activities in daily life. For example, in the home, the person is required to move about in narrow places, such as the kitchen, the toilet room, the bathroom, and the entrance. Outside, the person must move on various types of roads and footpaths and must move in/out of elevators and the like, and is also required to move about narrow spaces in various buildings, e.g., stations, and stairs and uneven paths. At most of these places, a movable chair such as a wheelchair is used.
As a movable chair of this type, a most widely used wheelchair has two front wheels and two rear wheels and is designed to allow a person to travel while supporting the person sitting on the seat on the large-diameter rear wheels. In addition, the small-diameter front wheels are designed to be steered, for example, to allow the wheelchair to travel in a desired direction. According to such a general wheelchair, the traveling direction can be relatively easily changed by steering the front wheels in a desired direction and rotating the rear wheels in opposite directions, i.e., forward and backward directions, respectively.
In recent years, the wheelchair as the above-descried movable chair has been improved with the development of the welfare society. However, there is room for improvement in the operability of the wheelchair.
More specifically, in the use of a movable chair of this type in daily activities, for a person who has a trouble with his/her legs or the like and cannot stand or walk by himself/herself, mounting/dismounting the chair is a burden and hence is performed with the aid of a helper.
In order to freely perform daily activities by using a such a movable chair, it is required that the center of gravity of a person be freely shifted when the person shifts his/her posture from a sitting posture to a lying posture while sitting on the chair or when the chair travels on a slope such as an upward or downward slope or travels over a stepped portion. However, a satisfactory means to accomplish this shift has not been invented. Therefore, there is a demand for some measure to satisfy these requirements.
In order to satisfy the above-described requirements, it is important to allow a person to mount/dismount the chair and change his/her sitting posture with a minimum force quickly.
It is also required that the above movable chair be easily folded to be carried when the person uses a transportation means such as a vehicle, a train, and an airplane. In addition, a reduction in size and weight of the movable chair is required.
In order to satisfy such requirements, for example, the following types of wheelchairs have been developed: a wheelchair having a back upholstery which can be tilted to a horizontal position; a wheelchair whose seat portion can be freely replaced; and a wheelchair constituted by a foldable bed. However, none of these wheelchairs employ a mechanism for accumulating potential energy in a spring when the seat portion of the chair is lowered, and using the energy to raise the seat portion of the chair. Therefore, new energy is required to raise the chair, and this operation cannot be quickly performed with a small force.
Furthermore, in the conventional wheelchairs and the like, since a folding mechanism is formed independently of a mechanism for vertically moving the seat portion of the chair, the structure of each mechanism is complicated, and an increase in weight and size is inevitably caused. Under the circumstances, demands have arisen for some measures to allow a person who has a trouble with legs or the like and cannot mount/dismount on/from the chair in a standing position by his/her own strength to easily mount/dismount on/from the chair without a helper.
In addition, when the above-mentioned wheelchair is to be folded, the seat must also be folded. Therefore, a material for the seat cannot be arbitrarily selected because the wheelchair seat should prevent spinal deformation and bedsores, adsorb vibrations, insulate the seated person and be comfortable. Careful consideration must be given to these points.
Furthermore, when the above-described movable chair is to be used as a wheelchair, the following points must also be considered. As conventional movable chairs of this type, movable chairs having various structures have been proposed, e.g., a chair using traveling devices having endless tracks such as crawlers to travel on stairs, slopes, and the like, a chair having such traveling devices attached, as auxiliary devices, to four wheels as main traveling devices, and a chair including sled-like traveling devices having sled-like frames as ground-contact portions to ensure good traveling characteristics and high stability.
However, a general wheelchair of the four-wheel type described above is vertically moved every time each wheel runs over an uneven portion, e.g., a recess or projection, or an obstacle on the track, thus making a person on the chair feel uncomfortable. In addition, the person consumes his/her energy for vertical movement to travel over such obstacles.
In order to travel over large obstacles, the radius of each wheel must be further increased, resulting in an increase in size of the overall wheelchair. Therefore, in order to solve such a problem, it is required that each traveling device be constituted by a device using an endless track such as a crawler or a sled type device.
Such devices will be described in detail below. If endless track or sled type traveling devices are used for a movable chair, the number of ground-contact points of the traveling devices exceeds four. Therefore, as compared with a four-wheel type movable chair, a movable chair of this type can ensure good traveling characteristics and high stability in traveling on tracks having uneven portions such as recesses and projections and obstacles.
According to a movable chair using endless track type traveling devices, for example, in order to travel over an obstacle, an angle defined by a vertical line extending from a contact point of an endless track with respect to the obstacle and a horizonal plane and an tangent on a curved ground-contact portion of the endless track at the contact point is only required to be larger than 0.degree.. Therefore, the problem of the increase in overall size is not posed, unlike the above-described four-wheel type movable chair. However, according to such an endless track type, since almost the entire surface of each crawler is brought into contact with the ground, the movable chair must travel over almost all the recesses and projections on the track, thus posing the problems of energy consumption for vertical movement and uncomfortable vertical motions.
According to the sled type traveling device, the chair can travel over obstacles and the like in the same manner as in the above-described endless track type, and the problem of the increase in size as in the four-wheel type is not posed. In addition, the sled type is simpler in structure than the endless track type. Furthermore, when the movable chair using the sled type traveling devices travels on the track having recesses and tracks, it moves forward while higher projections are interposed between sled. Therefore, energy consumption for vertical movement and vertical motions are small. However, the movable chair using the sled type traveling devices is greatly influenced by friction and the like between the ground-contact surfaces and the ground. In addition, when the chair travels over recesses and projections, forward/backward swinging motions are increased as the heights of the projections vary in the traveling direction. Furthermore, when the friction between the ground-contact surfaces and the ground is small, the movable chair using the sled type traveling devices tends to slide and hence is difficult to control.
On the other hand, since a movable chair of this type often travels on tracks having recesses and projections in traveling indoors and outdoors, it is required to minimize the energy consumption for vertical movement and vertical motions in traveling as well as reducing the overall size. In addition, it is required that a movable chair be smoothly moved in traveling, and that traveling control on stairs or a slope be performed in a predetermined state. Therefore, almost no movable chairs using endless track and sledge type traveling devices have been put into practice, although they are superior to a general four-wheel type wheelchair in traveling characteristics and stability. Under the circumstance, the advantages and disadvantages of various types of traveling devices for these conventional movable chairs must be reexamined as a whole, and some measures need to be taken to solve all the problems described above.
One of the problems posed in the above-described movable chairs using the endless track and sled type traveling devices is that none of these traveling devices can change their directions separately and independently at each ground-contact portion. If, therefore, such traveling devices are employed, a serious problem is posed in terms of a direction change operation.
More specifically, a movable chair having such traveling devices cannot change its traveling direction in the same manner as in the four-wheel type for the above-described reason. In order to change the traveling direction, the movable chair must be rotated about one ground-contact portion of one of the traveling devices by forcibly moving other ground-contact portions against the friction. This direction change operation is difficult to perform.
On the other hand, since movable chairs of this type often pass through narrow places indoors and outdoors, and are often required to change their traveling directions in such narrow places, as described above, the problem in direction change operations is a great obstacle to practical applications. For this reason, almost no movable chairs using endless track and sledge type traveling devices have been put into practice, although they are superior to a general four-wheel type wheelchair in traveling characteristics and stability. Therefore, some measures are required to easily perform such direction change operations.
For example, the traveling direction of traveling devices using endless tracks such as crawlers is changed by rotating the left and right crawlers in opposite directions. According to such endless track type traveling devices, however, the contact area between each crawler and the ground is large, and a large operating force is required to perform a direction change operation because the rotation of each crawler is hindered by the friction between the crawler and the ground, unlike a wheel-type movable chair. Especially on surfaces causing high frictional resistance, e.g., gravel, sandy, and snowy roads, direction change operations are difficult to perform. In addition, a floor surface is damaged by friction.